Childbirth is a common metaphor for artistic creation and, in the recent experience of the dramatist Joe Penhall, the two have blurred. "One night, I said to my wife: 'Guess what? I've just finished a play.' And she said: 'Guess what? I'm pregnant."

The child was their first, a son; the play, his ninth, is Haunted Child, opening at the Royal Court in London next week. As Penhall wryly notes, these days the gestation of a theatre production is somewhat longer than a pregnancy (because of waiting for stages, actors and directors to become free), and while waiting for Haunted Child to drop, there was time for a second son and another play. Birthday will open at the Court next May, giving him two premieres there in six months, believed to be a record for the venue.

The experience of coming relatively late (in his early 40s) to fatherhood has affected his recent writing. In Haunted Child, Sophie Okenedo plays a mother raising her young son alone after the disappearance of her partner. Birthday, in which Stephen Mangan will star, is a comedy set in a maternity ward, with a plot twist media outlets have been asked not to give away, so as to keep the surprise. Having read the play, I can only say that it presents on stage a novel and startling gynaecological image.

The two scripts are starkly different – Haunted Child has elements of a ghost story, Birthday employs devices from farce – but Penhall says this was accidental. After a long spell working in cinema, where the story is often summed up in a poster line before the film is even made, he experimented with writing more blindly. "With these two plays, I made a pact not even to ask myself what they were about until they were finished."

It's clear to me as a reader, though, that both deal with the extent to which a man takes responsibility for his offspring; one protagonist brutally opting out, the other brutally opting in. Penhall initially rejects this theory but then pauses, thinks and cackles. "Yeah. Yeah. I hadn't thought about that. But, yes, one guy does everything he possibly can to escape fatherhood and the other does everything he can to get involved."

Penhall's writing for theatre has been less frequent than might have been expected after the multi-award-winning success of Blue/Orange (2000), his National theatre writing debut, a tragi-comedy examining attitudes to mental illness through the case study of Christopher, a 24-year-old who claims to be the illegitimate son of the Ugandan dictator Idi Amin. This was followed by Dumb Show (2004) at the Royal Court, in which Douglas Hodge played a Barrymoresque comedian whose sexual and narcotic secrets are exposed in a tabloid sting.

Although Penhall is himself a former reporter (he began writing plays while at the South London Guardian), most critics reacted to his portrait of the British press in much the way that Vatican cardinals might review a drama about priestly sexual abuse. Few dramatists have moved so rapidly from critical darling to demon.

"It surprised me a little bit that the reviews were so partisan," Penhall says. "It did seem to hurt journalists' feelings. I thought: my God, they're like a giant family, even theatre critics somehow feel blood-related to the tabloids. But that play gets done all the time everywhere else and it's a nice little earner." He saw a hit production in Tokyo, played Kabuki style. "The only strange thing was that the audience was entirely female because, at 7.30pm, when it was on, all the men are still working."

His only other new play of the noughties was Landscape with Weapons (2007), at the National, in which a scientist who has created a revolutionary new weapon debates with his idealistic brother the morality of benefitting financially from it. In terms of reviews and box office longevity, the play continued the retreat from the peak of Blue/Orange. Was this hard to take? "Well, I began to notice that the plays that came after Blue/Orange were getting the same kind of response as the ones that came before it: full houses and happy audiences but lukewarm reviews. So, yes, I was surprised by it."

None of Penhall's major plays has more than four characters and many are three-handers, suggesting that trialogue is his natural form. "Yes," he laughs. "I have tried to do something about this. But I like the fact that it's pared down. I always want to boil everything right down. So now I've stopped being self-conscious about it and trying to plug another character in."

He denies it was disgruntlement with theatre that led him to concentrate on projects for TV (The Long Firm, adapted from Jake Arnott's novel, and Moses Jones, an original series) as well as movies, adapting Ian McEwan's Enduring Love and Cormac McCarthy's The Road. "I love film. But I haven't gone out looking for movie work. People have just asked me. I know people who have made so much money taking every whoring, sluttish, fucking rewrite job there is. And I don't want to be like that. If it gets frustrating, I just walk away. Because I've already got a job in theatre."

He did walk away from the film of Giles Foden's novel The Last King of Scotland, which shared with Blue/Orange a darkly comic fascination with Idi Amin. Despite five years' work on the script, the writer was happy, after a dispute with the producers, to have no credit on the final film."They wanted a film that was more commercial than my script. And that's not unusual. Everybody wants a script that's more commercial than I'm prepared to do. And the way to make it in film is to say yes to all the suggestions. Those are the guys they like. And I was really truculent."

He had a "fantastically happy experience" writing The Road but still clashed with the producers, Bob and Harvey Weinstein. During the US promotional tour of this bleak presentation of a post-apocalyptic America, Penhall told interviewers that the movie, which includes a sequence in an abandoned church, was a demonstration to Americans of "where Christian fundamentalism and George W Bush had got them". He recalls: "I thought I was being really clever. Because, in the UK, that kind of comment would be quotable. But they fucking hated it. I got hauled off the tour. The Weinsteins came to me and said: you're making people really angry and ruining our Oscar chances."

He remains "enormously proud" of The Road and tries only to take film work where he feels common values with the director; he's currently writing a cowboy movie for Sam Mendes and recently provided an uncredited script polish for Joe Wright on the child assassin movie Hanna.

But his main focus at the moment is theatre. As well as the Court premieres, he is working with Ray Davies on a musical using the songs of the Kinks. Despite a recession and cuts, drama is thriving, something Penhall attributes to a reaction against trends elsewhere in popular culture. "We're rediscovering that the pure theatrical form is beautiful and stunning. We're living in a viral cyber-age. Cinema is trying to reinvent itself with 3D and CGI and avatars. So the chance of seeing real people doing real things is newly exciting." Being in the audience for Jez Butterworth's Jerusalem struck him as "like being at Glastonbury. That's why Glastonbury's big as well. The visceral, live experience."

In common with Jerusalem, Penhall's new plays use long speeches, physical farce, coups de theatre. He increasingly supports the tautology that theatre must be theatrical: "I hate theatre where people are running round pretending they're at the beach or in a battle. Balls! Just make a film."

During rehearsals for Blue/Orange, Penhall wanted to cut a moment in which an orange is peeled on stage because he was concerned that it was clinically inaccurate. Roger Michell, the director, "insisted it would be a great theatrical moment. And I didn't believe him, but it was. You could smell the zest and see the spray. My favourite part of Landscape with Weapons is where the characters have a food fight, throwing curry at each other. There's something about those purely physical moments."

Penhall's plays frequently turn on one passionate argument being contradicted by another, and so it is no surprise when he starts worrying about the current popularity of theatre. "In the West End, it's a counterfeit boom: based on all these movie actors getting the idea to come and boost their credibility in the theatre. And a lot of the new writing boom is people writing about themselves. Norman Mailer once said we know so much about how sensitive liberal people think, but not enough about blue-collar workers and reactionaries. And the problem at the National, the Royal Court and Hampstead, is that you go and find yourself sitting in a sea of your own species."

• Haunted Child previews at the Royal Court, London SW1, from tomorrow; Birthday opens in May.